1. Field of the Invention
This invention relates in general to tread wheels for animals, and more particularly to a tread wheel useful for exercising dogs.
2. Description of the Related Art
A variety of tread wheels or drums have heretofore been proposed for exercising animals. Many patents teach the basic tread drum concept.
U.S. Pat. No. 1,794,951 (Freer), issued Mar. 3, 1931, appears to be the first true animal exerciser, and shows one of the two typical styles of "hamster wheel", with a shaft supporting a drum via a disk or spider on one side of the drum. The structure taught by this patent, and others like it, is designed for small animals such as hamsters, rats and the like, though the Freer patent indicates that it also can be used for foxes and other furbearing animals.
The Freer design would be very expensive and impractical to build and utilize for larger animals such as dogs. Given the weight of a dog, the cantilevered support required for a large version of Freer's side-mounted tread wheel would require mounting to a very solid wall or structure.
U.S. Pat. No. 4,088,094 (Howard) utilizes a similar side-supported drum concept, but the drum is supported from a movable base, and was designed mainly for exercising monkeys. However, the base again must be quite substantial due to the side-mounted arrangement for the drum, and it would not be easy to disassemble the apparatus or move it if the floor casters under the base could not be used (e.g., up a staircase).
The other basic design of "hamster wheel" supports the drum on a central shaft that extends through the drum or wheel, with spokes or a spider assembly on each side of the drum. The central shaft then is supported on each side of the wheel. U.S. Pat. Nos. 3,057,328 (Swartz), 3,682,477 (Harkins), 3,788,277 (Willinger et al.) and 3,933,126 (Gordon) provide examples. U.S. Pat. No. 528,066 (Ariens) is similar, though strictly speaking it is a working treadmill, not just an exercise device.
A tread wheel with a central shaft requires a much larger drum for a given size animal than a side-mounted drum, since the animal must run between the central shaft and the drum. However, this design has the advantage that a less substantial mounting structure can be used, since the drum is not cantilevered.
U.S. Pat. No. 3,994,262 (Suchowski et al.) combined the two foregoing concepts by splitting the central shaft in two. In this design, the drum is mounted on shafts on either side of the drum, but the shafts do not extend through the middle of the drum.
U.S. Pat. No. 2,681,638 (Carvell) teaches the basic concept of the "hamster ball", that is a non-stationary exercise drum or ball. In Carvell's design, an animal is caged inside a drum or ball which is then free to roll around on the floor as the animal runs inside the drum. While this might be cute with a hamster-sized drum or ball, with a dog-sized drum or ball the results could be disastrous.
U.S. Pat. No. 2,640,450 (Siegel) somewhat overcomes this drawback by rotatably mounting drums such as Carvell's in a stand. However, Siegel's structure would not be easily moved or disassembled if scaled up to accommodate a dog.
Finally, U.S. Pat. No. 883,485 (Ridgway) shows an amusement park treadmill drum for people. Even if scaled down to dog size, Ridgway's device is not easily disassembled or transported, and requires numerous special purpose components, increasing its cost.
The foregoing exercising tread wheels suffer from a number of disadvantages:
(a) Most of the tread drums have been designed primarily for small animals of the rodent variety. By virtue of their designs, they would be cumbersome and costly to produce on a scale large enough for a dog. Specifically, if made on a scale large enough to suit a dog, they would not assemble and disassemble readily for shipping and moving in and out of human size doors. Side-mounted drums would require excessively heavy-duty supports, and central shaft mounted drums would be excessively large.
(b) Most of the previous tread drums are supported either from one side or by a central shaft. Either technique requires a spider assembly and central bearing of some sort. The spokes of the spider present a dangerous pinch point for the animal, as well as any humans standing close by. They also effectively prevent a human handler from reaching into the drum while it is moving to encourage or otherwise assist the dog.